Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$55.54	10.213%	$61.2123	$61.21	$61.20	$61.20
Purchase #2	$107.72	10.457%	$118.9843	$118.98	$119.00	$119.00
Purchase #3	$201.90	6.547%	$215.1184	$215.12	$215.10	$215.10
Purchase #4	$75.74	8.764%	$82.3779	$82.38	$82.40	$82.40
Purchase #5	$203.81	10.666%	$225.5484	$225.55	$225.55	$225.50
Purchase #6	$155.25	10.546%	$171.6227	$171.62	$171.60	$171.60
Purchase #7	$127.80	5.386%	$134.6833	$134.68	$134.70	$134.70
7 purchase totals =	$927.76		$1,009.5473	$1,009.54	$1,009.55	$1,009.50